1. Technical Field of the Invention
The present invention relates to electrophoretic devices and manufacturing methods therefor, and more specifically, relates to an electrophoretic device in which an electrophoretic dispersion containing a dispersion medium and electrophoretic particles is accommodated between electrodes opposing each other.
In addition, the present invention relates to various electronic apparatuses each provided with an electrophoretic display device incorporating the above electrophoretic device.
2. Description of the Related Art
Hitherto, concerning electrophoretic devices in which an electrophoretic dispersion containing a dispersion medium and electrophoretic particles is accommodated between a pair of electrodes, application thereof to electrophoretic display devices has been known in which change in distribution of the electrophoretic particles caused by a voltage applied between the pair of substrates is used. FIG. 3(a) is a view showing the general structure of an electrophoretic display device to which an electrophoretic device is applied.
This electrophoretic display device 20 is composed of an electrode 3 formed on a first substrate 1, a transparent electrode 4 formed on a second substrate 2, an electrophoretic dispersion 10 filled between the electrode 3 and the transparent electrode 4, and a spacer 7 for preventing this electrophoretic dispersion 10 from flowing out. This figure shows a cross-section of one pixel of the display device.
The electrophoretic dispersion 10 is composed of a liquid-phase dispersion medium 6 and electrophoretic particles 5 dispersed in this liquid-phase dispersion medium 6. In addition, the liquid-phase dispersion medium 6 and the electrophoretic particles 5 are colored in different colors from each other.
To this electrophoretic display device 20, voltage sources 9a and 9b, which apply voltages in the direction opposite to each other, are connected via a switch 8. That is, the electrode 3 is connected to one end of each of the voltage sources 9a and 9b, and the electrode 4 is connected to the other end of each of the voltage sources 9a and 9b via the switch 8. When connection is formed as described above, by switching the switch 8, the direction of a voltage to be applied can be changed. By changing the direction of a voltage to be applied, the electrophoretic particles can be gathered at a desired electrode side, thereby performing a desired display.
That is, when the electrophoretic particles 5 are positively charged, as shown in (b) of the same figure, by applying a voltage of the voltage source 9a, the electrophoretic particles 5 can be gathered at the transparent electrode 4 side which is disposed close to an observer. In the state described above, the observer can view the color of the electrophoretic particles 5. On the other hand, as shown in (c) of the same figure, by applying a voltage of the voltage source 9b, the electrophoretic particles 5 can be gathered at the electrode 3 side which is disposed far from the observer. In the state described above, the observer views the color of the liquid-phase dispersion medium 6. When the electrophoretic particles 5 are negatively charged, the moving direction of the particles is opposite to that described above.
As described above, when the structure shown in FIG. 3(a) is employed, since two types of colors can be displayed in accordance with the direction of a voltage to be applied, an electrophoretic display device capable of displaying a desired image can be realized when the structure shown in the figure is disposed in every pixel.
In addition, an electrophoretic device having the structure in which an electrophoretic dispersion is enclosed in microcapsules has been known. When the device is thus formed, agglomeration of the electrophoretic particles and adhesion thereof to electrodes can be dissolved, and at the same time, handling of the dispersion system can be significantly improved during assembly.
However, in the case in which an electrophoretic dispersion is enclosed in microcapsules, gaps are formed between the capsules since the microcapsule has a spherical shape, and wall films of the microcapsules are not completely transparent, resulting in decrease in image contrast.
As means for solving the problems described above, for example, there has been a known technique for deforming microcapsules into a non-spherical shape. However, even when this technique is employed, it is difficult to totally eliminate gaps formed between the microcapsules, and the problem of presence of the microcapsule wall films cannot be dissolved.
The present invention was made in order to solve the shortcomings of the traditional technique described above, and a first object thereof is to provide an electrophoretic device and a manufacturing method therefor, in which a dispersion system is easily handled during assembly, and image contrast can be significantly improved.
A second object of the present invention is to provide an electronic apparatus incorporating a display device, in which image contrast can be significantly improved even when the display device is an electrophoretic display device.